The present invention relates to a liquid crystal display including an active matrix substrate furnished with a plurality of TFTs (Thin Film Transistors) in one-to-one correspondence with pixels, or a direct matrix substrate of an STN (Super Twisted Nematic) method, and driver ICs (Integrated Circuits) for driving individual pixels.
A liquid crystal display employing a liquid crystal display element of a nematic type has been used widely as a liquid crystal display of a numeric segment type, such as a watch and a calculator. Recently, the use of such a liquid crystal display has been extended to display means for a word processor, a computer, and a navigation system.
Because the liquid crystal display is advantageous over a CRT in an extreme thinness (small depth), small power consumption, and the ease in displaying a full color image, the liquid crystal display has been in increasing demand in diversified fields as a monitor for devices of a power-saving and space-saving type. A liquid crystal display of an active matrix type has been particularly popular as the foregoing liquid crystal display, in which active elements such as TFTs are used as switching elements and a matrix of pixels are provided.
FIG. 4 is a view schematically showing an arrangement of a conventional liquid crystal display. As shown in the drawing, the liquid crystal display includes an active matrix substrate 51, a print substrate (hereinafter, referred to as PCB (Printed Circuit Board) 52, and a plurality of FPCs (Flexible Printed Circuits)) 58 which connect the active matrix substrate 51 and PCB 52.
A matrix of pixel electrodes 53 are formed on the active matrix substrate 51. Further, TFTs 54 are formed on the active matrix substrate 51 as switching elements for selectively driving the pixel electrodes 53. The TFTs 54 are connected to the pixel electrodes 53 in one-to-one correspondence. In case of color display, although it is not illustrated in the drawing, color filter layers of red, green and blue and a black matrix that blocks light incident on the circumference of each pixel are additionally provided on the active matrix substrate 51 or a counter substrate.
The gate electrode of each TFT 54 is connected to one of a plurality of gate bus lines 55 and the source electrode thereof is connected to one of a plurality of source bus lines 56. The gate bus lines 55 and source bus lines 56 are aligned along a matrix of the pixel electrodes 53 in such a manner so as to cross each other at right angles. The TFTs 54 are driven under control when a gate signal is inputted via the gate bus lines 55, whereupon a data signal (display signal) is inputted to the pixel electrodes 53 via the source bus lines 56 through the TFTs 54.
Although it is not illustrated in the drawing, a counter substrate is provided to oppose the active matrix substrate 51, and a liquid crystal layer is placed in a space between the active matrix substrate 51 and counter substrate and sandwiched by the same. Further, a counter electrode is formed on the counter substrate, and an image is displayed as the orientation of liquid crystal molecules varies in response to a voltage applied across the counter electrode and each pixel electrode 53 in accordance with image data.
On the other hand, a driver IC 57 is provided to each FPC 58. In each FPC 58, connection portions to the PCB 52 are interconnected to each other by means of ACF (Anisotropic Conductive Film) and connection portions to the active matrix substrate 51 are also interconnected to each other by means of the ACF. The driver ICs 57 and the source bus lines 56 are connected to each other by means of the ACFs 59 formed on the active matrix substrate 51 side. Also, the driver ICs 57 are connected to input lines 61 and common connection lines 62 (described below) by means of the ACFs 59 formed on the PCB 52 side.
One end of the PCB 52 is connected to a control signal input FPC 60 used to input an external control signal, such as a reference clock and a data signal. The output terminal of the control signal input FPC 60 and the input terminal of one particular driver IC 57 are connected to each other by means of the input lines 61 formed on the PCB 52. Further, every two adjacent driver ICs 57 are connected each other at their corresponding electrode terminals by means of the common connection line 62 formed on the PCB 52.
In other words, the control signal inputted from the control signal input FPC 60 enters into one particular driver IC 57 via the input lines 61 and reaches the other driver ICs 57 via the common connection lines 62. Then, the data signal is inputted to each source bus line 56 from each driver IC 57 through the ACF 59.
However, in case of the above arrangement that the active matrix substrate 51 and PCB 52 are connected to each other by means of the FPCs 58 and that the input lines 61 and common connection lines 62 are formed on the PCB 52, the following problem will occur. That is, when the active matrix substrate 51 and PCB 52 are connected to each other by means of the FPCs 58, the active matrix substrate 51 and PCB 52 have to be spaced apart. This undesirably increases an frame edge portion, that is, an outside area of the actual display area, of the liquid crystal display.
Also, because the input lines 61 and the common connection lines 62 connecting the adjacent driver ICs 57 have to be formed on the PCB 52, the size of the PCB 52 itself has to be increased. This also causes the frame edge portion of the liquid crystal display to be increased.
The present invention is devised to solve the above problems and has an object to provide a light and inexpensive liquid crystal display having a small frame edge portion by reducing the size and weight of a mounting substrate furnished with driver ICs for driving pixels individually as an outboard substrate for a substrate furnished with a matrix of pixels thereon.
In order to fulfill the above and other objects, a liquid crystal display of the present invention is characterized by being furnished with:
a first substrate and a second substrate;
a liquid crystal layer sandwiched between the first substrate and second substrate;
data signal lines provided on one of the first substrate and second substrate;
scanning signal lines provided on one of the first substrate and second substrate;
a plurality of driver circuits for inputting a signal into the data signal lines and/or scanning signal lines; and
a plurality of mounting substrates which are provided with the plurality of driver circuits and connected to the first substrate and/or second substrate; and
common connection lines, provided on the first substrate and/or second substrate, for interconnecting the plurality of driver circuits.
According to the above arrangement, because each mounting substrate provided with the driver circuit is directly connected to the first substrate and/or second substrate, a total area of by the driver circuit section can be reduced compared with the case discussed in the prior art column where the active matrix substrate is connected to the PCB furnished with lines by means of the FPCs furnished with the driver ICs. Thus, not only can an area of the edge frame portion of the liquid crystal display be reduced, but also the weight thereof can be reduced. In addition, because fewer materials are used, the material costs can be saved. Moreover, because the number of steps in the manufacturing procedure is reduced, the manufacturing costs can be saved.
Also, because the common connection lines which interconnect the driver circuits are provided on the first substrate and/or second substrate, the size of the mounting substrates can be reduced compared with an arrangement by which the common connection lines are provided on the mounting substrates, for example. Thus, not only can the frame edge portion of the liquid crystal display be reduced further, but also the weight thereof can be reduced further.